This read-only counter tracks the total number of CLNP protocol data units received across every network interface running CLNP on this entity, including ones that turn out to be erroneous. An admin uses this as the top-level traffic-volume figure for CLNS activity, comparing its growth rate against more specific error counters to gauge what fraction of received traffic is problematic. For example, comparing this counter's growth against clnpInHdrErrors over the same interval would tell the admin what percentage of incoming CLNP traffic is arriving with header problems.